No well-designed, controlled studies have demonstrated the value of 'best practice' ergonomic interventions to reduce risk for musculoskeletal disorders and impairment among computer operators. Therefore, proposed guidelines for ergonomic and work organizational interventions have been challenged as having unproven benefit. The primary aim of this randomized controlled trial is to determine whether, over a 12 month period, a state-of-the-art ergonomic intervention package applied to 175 computer based customer service operators, is associated with an improvement in risk of upper extremity/neck musculoskeletal disorder, arm or neck pain-days, hand function, lost-time, and productivity in comparison to 175 controls subjects. Historical co-variates will be assessed with a baseline questionnaire and stability of co-variates will be verified with an exit questionnaire. The intervention will include an alternative geometry keyboard and mouse, large wrap around forearm rest, monitor location adjustment, vision check, chair adjustment, and training. The control group will receive a new conventional geometry keyboard and training. Upper extremity and neck pain severity, hand function and lost-time will be followed with a weekly questionnaire administered via the Internet. If a predetermined pain threshold is exceeded then a physical examination will be performed to determine whether or not a musculoskeletal disorder is present. Multivariate linear regression and logistic regression models will be applied examine main effects and to control for significant co-variates. The study is designed to detect a reduction of musculoskeletal incidence by half or a medium effect size (0.5SD) of the pain severity-week score. The total cost of implementing the intervention will be estimated. The findings and recommendations will be disseminated statewide in cooperation with the California Department of Health Services.